Ethernet interfaces are standard equipment in a wide range of computer systems, from embedded devices to mainframes. Moreover, switched Ethernet is deployed in a variety of environments, including home networks, office networks, data center networks, and campus networks. A key reason for switched Ethernet's wide-spread deployment is its ease of operation. First, Ethernet equipment will operate with little or no manual configuration. Second, switched Ethernet is self healing (e.g., it can automatically take advantage of redundant network connectivity to recover from network failures).
Switched Ethernet's ease of operation is derived in large part from its ability to flood packets throughout the network. Specifically, flooding enables a packet to reach the destination host's interface without any configuration of that interface or the network, regardless of the interface's location in the network topology. However, because Ethernet packets do not have a time-to-live field, the network topology must not have any cycles. Otherwise flooded packets will circulate endlessly inside the network cycles.